JEE Main 2026 — 21 January, Evening Shift — Question 68

MX is a sparingly soluble salt that follows the given solubility equilibrium at 298 K $\mathrm{MX}(\mathrm{s}) \rightleftharpoons \mathrm{M}^{+}(\mathrm{aq})+\mathrm{X}^{-}(\mathrm{aq}) ; \mathrm{K}_{\mathrm{sp}}=10^{-10}$ If the standard reduction potential for $\mathrm{M}^{+}(\mathrm{aq}) \xrightarrow{+\mathrm{e}^{-}} \mathrm{M}(\mathrm{s})$ is $\left(\mathrm{E}_{\mathrm{M}^{+} / \mathrm{M}}^{\Theta}\right)=0.79 \mathrm{~V}$, then the value of the standard reduction potential for the metal/metal insoluble salt electrode $\mathrm{E}_{\mathrm{X}^{-} / \mathrm{MX}(\mathrm{s}) / \mathrm{M}}^{\Theta}$ is $\_\_\_\_$ mV. (nearest integer) [Given: $\frac{2.303 \mathrm{RT}}{\mathrm{F}}=0.059 \mathrm{~V}$ ]